这是我第一次尝试通过 Certbot 更新 Let's Encrypt 证书。仔细阅读 Certbot 用户指南后，我创建了两个如下的 post hook 脚本：
root@pelargir:~# ls -l /etc/letsencrypt/renewal-hooks/post
total 8
-rwxr-xr-x 1 root root 697 Aug 29 16:35 10-setup-courier.sh
-rwxr-xr-x 1 root root 377 Aug 29 16:32 20-restart-services.sh
然后我在命令行上手动运行更新过程（即不通过 cron）。更新证书成功，但未能执行上述 post hook 脚本。这是相关的输出：
[...]
Running post-hook command: /etc/letsencrypt/renewal-hooks/post/10-setup-courier.sh
Hook command "/etc/letsencrypt/renewal-hooks/post/10-setup-courier.sh" returned error code 127
Error output from 10-setup-courier.sh:
/bin/sh: /etc/letsencrypt/renewal-hooks/post/10-setup-courier.sh: not found
Running post-hook command: /etc/letsencrypt/renewal-hooks/post/20-restart-services.sh
Hook command "/etc/letsencrypt/renewal-hooks/post/20-restart-services.sh" returned error code 127
Error output from 20-restart-services.sh:
/bin/sh: /etc/letsencrypt/renewal-hooks/post/20-restart-services.sh: not found
[...] …